Fibrous sheets coated or impregnated with biodegradable polymers or polymers blends

Abstract

Fibrous sheets are coated or impregnated with a biodegradable composition to render the sheets more resistant to penetration by liquids. Biodegradable polymer blends suitable for use in coating or impregnating a fibrous sheet can be manufactured from at least one “hard” biodegradable polymer and at least one “soft” biodegradable polymer. “Hard” biopolymers typically have a glass transition temperature of at least about 10° C. “Soft” biodegradable polymers typically have a glass transition temperature less than about 0° C. Another useful biodegradable polymer composition includes one or more biodegradable polymers and sufficient inorganic filler so as to render the treated sheet microwaveable. The biodegradable polymer compositions are especially well-suited for coating or impregnating paper sheets, e.g., 12–15 lb/3000 ft 2 tissue paper to yield food wraps. Food wraps will typically be manufactured to have good “dead-fold” properties so as to remain in a wrapped position and not spring back to an “unwrapped” form.

1. An article of manufacture that is adapted for use as a food wrap that is both resistant to liquids and biodegradable, comprising:
 a fibrous sheet comprised of thin, flexible tissue paper having a weight up to 15 lb/3000 ft 2  prior to being coated or impregnated with any thermoplastic polymers, 
 at least a portion of the fibrous sheet being coated and/or impregnated with a biodegradable composition that renders the fibrous sheet more resistant to liquids and that yields an article that is adapted for use as a food wrap such that it is sufficiently thin and flexible so as to be easily wrapped around a food item and that possesses sufficient dead-fold that it will remain wrapped around the food item absent application of an external force, the biodegradable composition comprising:
 at least one soft thermoplastic biodegradable polymer having a glass transition temperature less than about 0° C.; and 
 at least one stiff thermoplastic biodegradable polymer having a glass transition temperature of at least about 10° C. 
 
 
     
     
       2. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer comprises at least one member selected from the group consisting of polylactic acid, polylactic acid derivatives, and a modified polyethylene terephthalate in which a portion of the terephthalate groups are substituted with at least one aliphatic diacid. 
     
     
       3. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer comprises at least one of a polyesteramide, a polyhydroxybutyrate having a glass transition temperature of at least about 10° C., a terpolymer including units formed from glycolide, lactide and ε-caprolactone, or a polyesteramide formed from at least one diacid, at least one diol, and at least one amino acid. 
     
     
       4. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer comprises at least one of a polylactic acid or a polylactic acid derivative. 
     
     
       5. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer comprises at least one of an aliphatic-aromatic copolymer, an aliphatic polyester including units formed from at least one of a lactide or a hydroxyacid having at least 4 carbon atoms, polyhydroxybutyrate, a polyester including units formed from succinic acid and an aliphatic diol, polycaprolactone, polyhydroxybutyrate-hydroxyvalerate copolymer, polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, or thermoplastic starch. 
     
     
       6. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer comprises at least one of an aliphatic-aromatic copolyester including units formed from an aliphatic diol, an aliphatic diacid and an aromatic diacid or an aliphatic-aromatic copolyester including units formed from adipic acid, dialkyl terephthalate, and at least one aliphatic diol. 
     
     
       7. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer is included in a range of about 20% to about 99% by weight of the biodegradable composition. 
     
     
       8. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer is included in a concentration of at least about 40% by weight of the biodegradable composition. 
     
     
       9. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer is included in a concentration greater than 50% by weight of the biodegradable composition. 
     
     
       10. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer has a glass transition temperature of at least about 15° C. 
     
     
       11. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer has a glass transition temperature of at least about 25° C. 
     
     
       12. An article of manufacture as defined in  claim 1 , wherein the stiff thermoplastic biodegradable polymer has a glass transition temperature of at least about 35° C. 
     
     
       13. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer is included in a concentration up to about 70% by weight of the biodegradable composition. 
     
     
       14. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer is included in a concentration less than 50% by weight of the biodegradable composition. 
     
     
       15. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer is included in a concentration up to about 45% by weight of the biodegradable composition. 
     
     
       16. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer has a glass transition temperature less than about −4° C. 
     
     
       17. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer has a glass transition temperature less than about −10° C. 
     
     
       18. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer has a glass transition temperature less than about −20° C. 
     
     
       19. An article of manufacture as defined in  claim 1 , wherein the soft thermoplastic biodegradable polymer has a glass transition temperature less than about −30° C. 
     
     
       20. An article of manufacture as defined in  claim 1 , the biodegradable composition further comprising at least one particulate filler. 
     
     
       21. An article of manufacture as defined in  claim 20 , the particulate filler being included in an amount so as to render the article of manufacture microwaveable. 
     
     
       22. An article of manufacture as defined in  claim 20 , the particulate filler being included in an amount of at least about 10% by weight of the biodegradable composition. 
     
     
       23. An article of manufacture as defined in  claim 20 , the particulate filler being included in an amount of at least about 20% by weight of the biodegradable composition. 
     
     
       24. An article of manufacture as defined in  claim 20 , the particulate filler being included in an amount of at least about 30% by weight of the biodegradable composition. 
     
     
       25. An article of manufacture as defined in  claim 20 , the particulate filler comprising at least one of silica, calcium carbonate, clay, talc, mica, alumina, or ceramic. 
     
     
       26. An article of manufacture as defined in  claim 1 , the biodegradable composition comprising a film or sheet that has been laminated to at least one side of the fibrous sheet. 
     
     
       27. An article of manufacture as defined in  claim 1 , the thin, flexible tissue paper comprising 12–15 lb/3000 ft 2  tissue paper prior to being coated or impregnated with the biodegradable composition. 
     
     
       28. An article of manufacture that is adapted for use as a food wrap that is both resistant to liquids and biodegradable, comprising:
 a fibrous sheet comprised of thin, flexible tissue paper, 
 at least a portion of the fibrous sheet being coated and/or impregnated with a biodegradable composition that renders the fibrous sheet more resistant to liquids and that yields an article that is adapted for use as a food wrap such that it is sufficiently thin and flexible so as to be easily wrapped around a food item and that possesses sufficient dead-fold that it will remain wrapped around the food item absent application of an external force,
 the biodegradable composition comprising at least one member selected from the group consisting of polyhydroxybutyrate, polylactic acid, and aliphatic-aromatic copolymers and at least about 20% by weight of a particulate filler. 
 
 
     
     
       29. An article of manufacture as defined in  claim 28 , the thin, flexible tissue paper having a weight of up to 15 lb/3000 ft 2  prior to being coated or impregnated. 
     
     
       30. An article of manufacture as defined in  claim 28 , the thin, flexible tissue paper comprising 12–15 lb/3000 ft 2  tissue paper prior to being coated or impregnated. 
     
     
       31. An article of manufacture as defined in  claim 28 , the biodegradable composition comprising at least about 30% by weight of an inorganic filler. 
     
     
       32. An article of manufacture as defined in  claim 31 , the inorganic filler comprising at least one of silica, sand, crushed rock, bauxite, granite, limestone, sandstone, glass beads, aerogel, xerogel, mica, clay, alumina, kaolin, microspheres, hollow glass spheres, porous ceramic spheres, gypsum, insoluble salts, calcium carbonate, magnesium carbonate, calcium aluminate, magnesium carbonate, titanium dioxide, talc, ceramic, zirconium compounds, xonotlite (a crystalline calcium silicate gel), lightweight expanded clay, perlite, vermiculite, pumice, zeolites, minerals, or other geologic material. 
     
     
       33. An article of manufacture that is adapted for use as a food wrap that is both resistant to liquids and biodegradable, comprising:
 a fibrous sheet comprised of thin, flexible tissue paper, 
 at least a portion of the fibrous sheet being coated and/or impregnated with a biodegradable composition that renders the fibrous sheet more resistant to liquids and that yields an article that is adapted for use as a food wrap such that it is sufficiently thin and flexible so as to be easily wrapped around a food item and that possesses sufficient dead-fold that it will remain wrapped around the food item absent application of an external force, the biodegradable composition comprising:
 at least one biodegradable polymer comprising at least one member selected from the group consisting of polyesteramides, polyhydroxybutyrate, terpolymers including units formed from glycolide, lactide and ε-caprolactone, polylactic acid, polylactic acid derivatives, aliphatic polyesters, polyesters including units formed from succinic acid and an aliphatic diol, polycaprolactone, polyhydroxybutyrate-hydroxyvalerate copolymer, polybutylene succinate, polybutylene succinate adipate, polyethylene succinate, thermoplastic starch, aliphatic-aromatic copolyesters including units formed from an aliphatic diol, an aliphatic diacid and an aromatic diacid and having a glass transition temperature less than about 0° C., and aliphatic-aromatic copolyesters including units formed from adipic acid, dialkyl terephthalate, and at least one aliphatic diol and having a glass transition temperature less than about 0° C.; and 
 at least one inorganic filler included in a concentration of at least about 20% by weight of the biodegradable composition. 
 
 
     
     
       34. An article of manufacture as defined in  claim 33 , wherein the biodegradable composition comprises at least one soft biodegradable polymer having a glass transition temperature less than about 0° C. 
     
     
       35. An article of manufacture as defined in  claim 34 , wherein the biodegradable composition further comprises at least one stiff biodegradable polymer having a glass transition temperature of at least about 10° C. 
     
     
       36. An article of manufacture as defined in  claim 34 , wherein the biodegradable composition comprises silica as the inorganic filler. 
     
     
       37. An article of manufacture as defined in  claim 36 , wherein the article of manufacture is microwaveable. 
     
     
       38. An article of manufacture as defined in  claim 33 , the thin, flexible tissue paper comprising 12–15 lb/3000 ft 2  tissue paper. 
     
     
       39. An article of manufacture that is adapted for use as a food wrap and that is both resistant to liquids and biodegradable, the article manufactured according to a process comprising:
 providing a fibrous sheet comprised of thin, flexible tissue paper; and 
 coating and/or impregnating at least one side of the fibrous sheet with a thermoplastic biodegradable composition that includes a biodegradable polymer at least about 20% by weight of a particulate filler in order to render the fibrous sheet more resistant to liquids and to yield an article that is adapted for use as a food wrap such that it is sufficiently thin and flexible so as to be easily wrapped around a food item and that possesses sufficient dead-fold that it will remain wrapped around the food item absent application of an external force. 
 
     
     
       40. An article of manufacture as defined in  claim 39 , the process for manufacturing the article further comprising:
 heating the thermoplastic biodegradable composition so as to form a thermoplastic melt comprising an initially flowable composition; 
 applying the thermoplastic melt to at least one side of the fibrous sheet so as to coat or impregnate the fibrous sheet; and 
 allowing the thermoplastic melt to harden. 
 
     
     
       41. An article of manufacture as defined in  claim 40 , wherein the thermoplastic melt is applied to the at least one side of the fibrous sheet using a doctor blade or by spraying. 
     
     
       42. An article of manufacture as defined in  claim 41 , wherein the thermoplastic melt has a melt flow index of at least about 40 g/10 min. 
     
     
       43. An article of manufacture as defined in  claim 41 , wherein the thermoplastic melt has a melt flow index of at least about 70 g/10 min. 
     
     
       44. An article of manufacture as defined in  claim 41 , wherein the thermoplastic melt has a melt flow index of at least about 100 g/10 min. 
     
     
       45. An article of manufacture as defined in  claim 39 , the process for manufacturing the article further comprising:
 heating the thermoplastic biodegradable composition so as to form a thermoplastic melt comprising an initially flowable composition; 
 forming a sheet or film from the thermoplastic melt; and 
 laminating the sheet or film to at least one side of the fibrous sheet. 
 
     
     
       46. An article of manufacture as defined in  claim 45 , wherein the sheet or film is formed by at least one of casting, extrusion or blowing. 
     
     
       47. An article of manufacture as defined in  claim 46 , wherein the sheet or film is laminated to the fibrous sheet by co-extrusion. 
     
     
       48. An article of manufacture as defined in  claim 39 , the thin, flexible tissue paper having a weight of up to 15 lb/3000 ft 2  prior to being coated or impregnated. 
     
     
       49. An article of manufacture as defined in  claim 48 , the thin, flexible tissue paper comprising 12–15 lb/3000 ft 2  tissue paper prior to being coated or impregnated.